Amplifier



April 10, 1928. 1,665,699

E. w. GRAEF AMPLIFIER Filed Feb. 12, 1924 IN VEN TOR A TTORNE Y Patented Apr. 10, 1928.

UNITED STATES ERNEST W. GRAEF, OF CALDWELL, NEW JERSEY.

marries.

Application filed February 12, 1924. Serial No. 892,287.

My invention relates to improvements in sound amplifiers or horns of the class in which sounds or sound waves are increased or magnified.

An object of my invention is to provide a sound amplifier or horn of the class speci-..

lied which shall have the characteristics of reproducing and amplifying or magnifying sounds entering the same without distortion and with mellowness, to the end that the original sounds will be reproduced with the same tones but with increased volume without, however, assuming metallic or raucous qualities, whereby high and low tones will not become mixed ordistorted and will be transmitted from the device substantially in their original significance or rendering.

My invention is particularly applicable as a reproducing horn or device, such as commonly called a loud speaker, to increase sounds or tones transmitted from-the receivers of radio or wireless apparatus, al-

though the -horn is also applicable to the reception and transmission of sounds from other instruments, such as talking machines, telephone receivers, megaphones and the like, as well as human sounds directly admitted into the amplifier.

My invention comprises novel details of improvements that will be more fully hereinafter set forth and then pointed out in the claims.

Reference is to be had to the accompan in drawings forming a part hereof, wherein ig. 1 is a front view illustrating a convenient form of sound amplifier or horn embod in my invention;

ig. is a. cross section on 1; and

Figs. 3 and 4 are vertical sections respec tively on line b, b, in Fig. 2, Fig. 3 looking line a, a, in Fig.

toward the bottom of the sheet and Fig. 4.

looking toward the top of the sheet.

Similar numerals of reference indicate corresponding parts in the several views.

My improved sound amplifier or horn indicated generally atl, as illustrated, comprises a block or mass of relatively solid material, preferably moulded or cast from suitable material, and provided with apassage 2 for sound or sound waves within the same having a relatively small inlet opening at 3 and a relatively large or wide mam outlet opening at 4, which passage graduall increases in diameter or tapers from the inlet to the main outlgt. In the example illustrated the passage 2 is curvilinear and convolute, the inlet opening 3 being shown opening through one side or wall preferably toward the bottom 1 of the body 1, and the main outlet 4 is shown opening through a side or wall 1 at an angle to the wall or bottom 1, and at an angle to the plane of passage 2. The device is adapted to stand upon a surface and is shown provided with short projections or feet 5 on the side of bottom 1, through which the opening 3 enters, the main or large sound delive outlet 4 being in the side wall facing the user in ,usual practise. The main outlet 4 is formed in saidwall 1 in such a manner as to diverge outwardly. At 6. is a secondary soundoutlet opening communicating with passage 2 and located between the inlet 3 and main outlet 4, being shown located nearer the main outlet 4 than the inlet 3. By preference the seconda outlet 6 opens through the space within t e main body 1 that is provided within the rim portion 1 in the front wall 1" around the main outlet 4. The inner wall 1 of passage 2 terminates adjacent to main outlet 4 in such a way as to permit free flow of sounds or sound waves .made of any suitable material. A cementitious material gives good results, such as Portland cement, plaster Paris or the like,

moulded or, cast in a solid mass, either in a single piece or in two or more parts secured together in block-like formation by ang suitable means. In making the am li or or horn suitable outer separable moul sections may be'provided within which a suitable core for the passage 2, .(to provide its'inlet 3, outlet 4 andsecondary outlet 6), may be supported in any well known way. The core may be made of suitable material, such as wax or parafiin, suitably supported withmore or less nonin the mould sections and adapted to be melted for removal from the cast material or the core may be made of rubber adapted to stretch so that it may be pulled from the cast material through the large opening 4 after the material has suitably set or hardened. The core may have a projection for producing opening 6. Although I have referred to making the amplifier or horn of cementitious material it will be understood that it may be made of any other desired material suitable for the purpose intended,

such as paper, wood or the like. of such bulk that the sound waves will not cause vibra tion or ringing of the mass.

The inlet opening 3 may be suitably connected with any desired sound-producing instrumcnt, such as any well known receiver 7 of a radio or wireless set of instruments. or may communicate with the sound box of a talking machine or any other instrument from which sounds or sound waves are transmitted or the inlet 3 may be used to transmit human vocal sounds, as in the nature of a megaphone or kindred instrument. In the example illustrated the body 1 is provided with a recess 8 in its lower surface, shown in one of the projections or feet 5, in which the receiver 7 is located. As shown in Fig. 3,

the usual ear piece 7 of the receiver is provided with holes to receive screws 9 which are screwed into the body 1 (or into nuts that may be moulded or set in the body), whereby the receiver 7 is secured with its sound outlet opposing the inlet opening 3 of the body 1,-and is located in a secure place not visible from the front of the device.

In accordance with my improvements the sounds or tones which enter the passage 2 through the small end thereof will be amplified or increased for emission through the main outlet 4 in the manner before described so as not to be distorted or rendered raucous. One of the advantages of my invention is that'low tones or sounds and high tones or sounds will not become mixed in passage 2 in such a manner'as to create undesired sounds, my present theory being that the small secondary opening 6 acts as a relief for the sound waves, keeping the waves from.

messes mixing just before they would tend to become cavernous by their expansion at the large opening. My improvement may be likened to the human or animal throat and nasal passages, in that the passage 2 with its large outlet opening 4 and the smaller secondary outlet 6 serve in the nature of the animal vocal passage, to relieve the pressure or vibration of sound waves within passage 2, whereby the sound vibrations within passage 2 are relieved as may be required for the amplified or magnified"reproduction of the original tones or sounds substantially unchanged in characteristics, although pleasing to the ear of the listener. I am unable to state more definitely than above the reasons why my improved amplifier or horn amplifies or magnifies sounds or tones sub stantially without distortion and Without producing discordant and raucous rendition of vocal or instrumental tones. and for the present rely for an explanation upon the analogy to the animal sound-producing organs which I have mentioned.

Having now described my invention what I claim is:

1. An amplifier of the character specified comprising a body having an interior passage provided with an inlet and an outlet, said passage gradually increasing in diameter from the inletto the'outlet and being arranged in convolute form with the main outlet opening through one side of the body in a position transverse to the plane of the passage and a secondary outlet opening through the same side as the main outlet.

2. An amplifier of the character specified comprising a-relatively solid body having a base and having an interior passage provided with an inlet opening through the base and a main outlet larger than the inlet opening through a diflerent wall, said body having a'recess in the base communicating with said inlet, said recess being adapted to receive an electrical sound transmitting instrument.

ERNEST W. GRAEF. 

